HEIDENHAIN NC 124 - Manual (Page 13)

1 Fundamentals of Positioning
TNC 124 13
Fig. 1.7: Position definition through incremental
coordinates
Incremental workpiece positions
A position can also be referenced to the preceding nominal posi-
tion. In this case the relative datum is always the last pro-
grammed position. Such coordinates are referred to as incre-
mental coordinates (increment = increase). They are also
called incremental or chain dimensions (since the positions are
defined as a chain of dimensions). Incremental coordinates are
designated with the prefix I .
Example: Incremental coordinates of position 3 referenced to
position 2
Absolute coordinates of position 2 :
X = 10 mm
Y = 5 mm
Z = 20 mm
Incremental coordinates of position 3 :
I X = 10 mm
I Y = 10 mm
I Z = –15 mm
If you are drilling or milling a workpiece according to a drawing with
incremental coordinates, you are moving the tool by the value of the
coordinates.
Absolute workpiece positions
Each position on the workpiece is uniquely identified by its absolute
coordinates.
Example: Absolute coordinates of the position
1 :
X = 20 mm
Y = 10 mm
Z = 15 mm
If you are drilling or milling a workpiece according to a workpiece
drawing with absolute coordinates, you are moving the tool to the
value of the coordinates.
Datums and Positions
Y
X
Z
1
20
10
Z=15mm
X=20mm
Y=10mm
15
I
Z=–
15mm
Y
X
Z
2
10
5 5
15
20
10
10
I X=10mm
I
Y=10mm
3
0
0
Fig. 1.6: Position definition through absolute
coordinates